Republican Senate candidate Daniel B. Winslow, who has suggested that he is a member of the middle class, earned more than $500,000 a year in both 2010 and 2011, making him part of the top 1 percent of earners in America.

Winslow, a state representative and trial lawyer, released the information in a one-page memo that showed his annual earnings and the federal tax rate he paid every year between 2003 and 2011. With his memo, he became the first candidate to inject the issue of tax returns into the special election.

Winslow said he was disclosing the information as part of his pledge to be transparent and promised to release 10 years of complete tax returns next week.

But the filings also seemed designed to quietly amend the portrait he has painted of himself as a typical workaday earner. In addition, the disclosure — on a snowy Friday afternoon, when much of the news media and the public were focused on the storm — suggested that it may have been timed to avoid broad public scrutiny.

“Throughout my campaign I will endeavor to promote openness, clarity of opinion, and transparency,” Winslow said in a statement. “In this condensed election cycle we owe it to the voter to be forthright about our views and our financial records so that when they go to the polls they have adequate information to make an informed choice.”

When contacted by the Globe, only one of the five other candidates in the race, Republican Michael J. Sullivan, a former US attorney, said he was planning to match Winslow in releasing 10 years of tax returns. The third Republican in the race, Gabriel E. Gomez, would not say if he would release his returns.

Winslow’s move may be designed to pressure Gomez to do so, since Gomez has until recently been working as a private equity investor, a highly lucrative field that enjoys special tax benefits.

Winslow’s earnings may come as a surprise to voters who have heard him on the campaign trail, where he talks about the two mortgages and three tuitions he has to pay. He also mentions that his father was an antenna repairman and his mother was a nurse.

“The Senate has plenty of millionaires, but I think we need more senators who have mortgages to pay, and who have walked in the shoes of the working men and women of Massachusetts, who come from the middle class,” he said at a press conference last month.

A former district court judge, onetime chief legal counsel to Governor Mitt Romney and, until recently, a litigator at the firm Proskauer, Winslow lives in Norfolk and owns a second home in Truro.

He recently loaned his campaign $100,000 to help finance paid signature gatherers so he could qualify for the Republican primary ballot.

He reported an average adjusted gross income of $318,473 between 2003 and 2011. He earned a low of $115,586 in 2003 and highs of $514,745 in 2010 and $567,749 in 2011. His average federal tax rate was 22.2 percent.

Sullivan’s campaign did not make clear when he would release 10 years of tax returns, but urged Gomez to disclose his finances as well.

“Mike would be happy to be transparent, and we would encourage Mr. Gomez to do the same,” said Paul Moore, Sullivan’s campaign manager. “Mike’s been a public servant during most of the last 10 years, so it’s not been years of raking in millions.”

Gomez’s campaign said some of his financial information will be released in the personal financial disclosure forms all federal candidates must complete by March 30.

On the Democratic side, aides to US Representatives Edward J. Markey and Stephen F. Lynch said their campaigns had not decided whether to release tax returns. The base salary for a member of the US House is $174,000.

“Unlike Dan Winslow, congressman Lynch is a full-time legislator and does not have a second job,” said Lynch spokesman Conor Yunits. “As a member of Congress, his salary is publicly available and he has already made a full public disclosure of his income and assets.”

Giselle Barry, a Markey spokeswoman, said in a statement: “Rep. Markey’s income, assets, liabilities, and transactions for the past 20 years are publicly available to anyone who wants to see them from the disclosure forms he files each year. He believes a reasonable level of tax disclosure is appropriate and is considering the issue carefully.”

Tax returns often become flash points in political campaigns because they show where candidates fall on the income scale and whether they use loopholes or benefits to reduce their tax burdens below what the typical middle-class earner might pay. The returns may also reveal conflicts of interest and contradictions between a candidate’s policy pronouncements and personal financial practices.

During last year’s presidential race, for instance, Mitt Romney faced a firestorm of criticism for not releasing multiple years of tax returns. Critics accused the multimillionaire of trying to exploit tax loopholes to avoid paying his fair share to the government.

In last year’s Senate race in Massachusetts, Elizabeth Warren and Scott Brown both released tax information that showed they were in the nation’s top income bracket.